Colin Cunningham appeared in some 15 episodes of Stargate SG-1, as Major Paul Davis. When he turns up here in the midst of the impending Wraith attack on Earth, it’s his one and only appearance on Stargate Atlantis.

We’ve seen Wraith drain human victims to the brink of death, and then restore their life and youth again (“Common Ground”) — but this episode is the first time we see someone pretty much dead (Ronon) who is resurrected by a Wraith’s ability. It added an interesting wrinkle in a potential alliance with Todd, had the series continued.

Colonel Caldwell mentions in passing that the Earth cruiser Odyssey is off on a super-secret mission. Producers eventually confirmed that this was an oblique set-up for Stargate Universe: the Odyssey crew was searching for a naquadria-rich planet capable of supporting the Icarus Project and the plan to dial the 9-chevron address.

Despite the fact that “Enemy At the Gate” wasn’t intended to be the show’s final episode, thematically the return to Earth makes for a nice bookend to the series. The Ancient city hasn’t sat on the surface of the Earth since the first scene of the first episode (“Rising, Part 1”).

Though SGA was cancelled in 2008, Syfy Channel quickly announced that it planned to air a direct-to-DVD movie — potentially the first of an ongoing series of movies. But eventually, when the DVD market continued to soften and MGM plunged into bankruptcy, all plans for Stargate: Extinction and future films were shelved indefinitely.